The invention relates to a method and a device for controlling and supervising a hybrid vehicle of the type comprising four drive wheels. More particularly, the invention relates to a method and a device for controlling and supervising a rear axle unit of a hybrid vehicle with four drive wheels, having as vehicle propulsion and/or traction means at least one electric machine supplied by a high-voltage battery and an engine. The method makes it possible to retranscribe the driver's desire, such as a depression of the accelerator pedal, into control settings to be dispatched to electrical and mechanical actuators.
The advantages of electric vehicles are known and originate in particular from the silent and non-polluting nature of their motor. The question of the recharging of their battery is substantially improved by hybrid vehicles which make it possible to reach autonomy and performance levels that are hardly achievable in the case of a purely electric vehicle.
The technical problem underlying the invention has been identified by the applicant within the framework of studies on new hybrid vehicles with four drive wheels and equipped with an independent mechanical power source on each axle unit. The front axle unit of the vehicle is driven by a conventional power train with an internal combustion engine and a manual, robotized or automatic gearbox. The rear axle unit is driven by an electric actuator which is an electric machine capable of providing a torque and power to the wheel by way of a differential. The energy storage element comprises a battery for providing or receiving energy coming from the electric machine operating either as a motor, or as a generator. Thus, the electric machine operating as a motor is capable of providing a required torque and power to the wheels of a given axle unit.
The engine associated with the electric motor in this kind of hybrid vehicle makes it possible either to add extra power for on-road journeys, or to recharge the battery either with the aid of a current generator or with the aid of the electric motor when it is reversible and is operating as a generator.
In the prior art, the supervision of a hybrid vehicle implements a supervision function which makes it possible to transform the driver's desire into control settings to be dispatched simultaneously to the electric machine and to the engine. Such supervision must also ensure a minimum safety of the behavior of the vehicle such as the command of the rear axle unit so as to satisfy a stability criterion of the vehicle when it operates in “four-wheel drive” mode. The supervision device must also ensure the safety of the electrical items such as the high-voltage battery and the electric machine, particularly the control of the admissible power under charge and under discharge through the battery.
Solutions for supervising the management of the controls of the hybrid vehicle with an axle unit equipped with an electric motor and an axle unit equipped with an engine are known in the prior art. Document US-2002/0057582 describes and represents a controller for managing the electrical power supply of such a hybrid vehicle. But this controller only makes it possible to limit the conversion of electrical energy coming from the battery which supplies in particular the electric machine so as to forestall excessive discharging of the battery and to protect the electrical items of the vehicle. The controller acts simultaneously on the control of the electric machine and on that of the engine.
Though document US-2002/0057582 provides for a solution for protecting the electrical items of a hybrid vehicle, it does not make it possible to supervise at the same time the behavior and the stability of the vehicle driven by four drive wheels.